The crime scene in the December homicide (Philadelphia Police Department)

Posted: Jan 12 2016 03:48PM EST

Updated: Jan 12 2016 03:48PM EST

PHILADELPHIA- WTXF - The mayor’s office has announced a $20,000 reward for the arrest and conviction of the suspect in a Southwest Cedar Park homicide from December, in which a man was shot while walking his dogs.

On December 16, police responded to a shooting on the 4600 block of Kingsessing Avenue, where 34-year-old Mark Marshall was found with multiple gunshot wounds. The victim was transported to Presbyterian Hospital where he was pronounced dead.

An unknown black male exited the passenger side of a Dodge/Chrysler minivan, approached the victim- who was walking two dogs- and engaged in argument. Police say the suspect followed the victim and then shot him.

The suspect is described as a black male, 20-30 years of age, a height between 5’7” and 5’10”, with a medium build and beard. He was wearing a light color-hooded sweatshirt and orange wool hat.

Those with information are asked to call 215.686.TIPS (8477) or text a tip to PPD TIP or 773847.